The two main characters are set part in their respective movies by a few hundred years, so I don't know HOW this would work, or how the comic worked.

First of all, Hollywood has made it abundantly clear that films don't have to make sense. I wouldn't count on there being a shred of continuity between this project and any previous Alien or Predator films.

However, should some studio exec actually care enough to place this in some kind of franchise continuity, it would have to be set after Ripley's adventures since the treatment mentions a team of scientists on "an expedition to Antarctica to lure Predator hunters, using Alien eggs as bait." (Why a group of scientists would embark on such an endeavor is beyond me.)

I just can't get excited about this project now. It would be one thing if Ripley was included and somehow teamed up with a faction of Predators to rid the Earth of this Alien threat once and for all, but as a stand alone project, possibly set outside continuity, I have a bad feeling about this.